
Nate T. answered 01/31/20
Electrical Engineer with Experience Tutoring Math and Physics
Hi Jen!
When you're paddling a canoe in a current, the water will either increase or decrease your speed by exactly the speed of the current.
Examples:
(with the current)
if you normally paddle 1 mile per hour and the current is pushing you forward at 1 mile per hour, your total speed will be 2 miles per hour.
(against the current)
if you normally paddle at 1 mile per hour and the current is pushing you back at 1 mile per hour, your total speed will be 0 miles per hour (you wont move).
For this problem:
he normally canoes at 6 mph.
Speed is the distance traveled divided by time it takes to get there. In this case, he traveled 8 miles in 2 hours. 8 miles ÷ 2 hrs = 4 miles per hour.
So, if he normally paddles at 6 mph but his total speed is 4 mph, the current has slowed him down by exactly 2 mph. Therefore, the current speed is 2 mph.